Mechanistic Insights of Zn-Ion Storage in Synergistic Vanadium-Based Composites

A novel composite material Na2V6O16 center dot 3H2O-AlxV2O5 (NVO-AVO) is designed and synthesized for the first time in aqueous zinc ion battery cathode. The electrochemical behavior is elucidated in detail using in situ and ex situ techniques. The NVO-AVO is simple, inexpensive, and safe to fabricate and contributes to the synergistic effect of orthorhombic AlxV2O5 (AVO) and monoclinic Na2V6O16 center dot 3H2O (NVO), the NVO-AVO composites have fast Zn2+ kinetics and exhibit good electrochemical properties. At 300 mA g-1, the specific capacity is as high as 392.5 mA h g-1, and even more excitingly, NVO-AVO remains a specific capacity of 160.6 mA h g-1 even after 18 300 cycles at 5000 mA g-1, which is significantly better than the stability of both NVO and AVO. The distinctive V3O8 layered structure in Na2V6O16 center dot 3H2O facilitates the diffusion of Zn2+, and structural water located between the V3O8 layers facilitates rapid charge transfer by widening the gallery spacing and supposing more storage sites for Zn2+. In addition, AlxV2O5 forms [AlO6] octahedral units that enhance structural stability and play a crucial role in maintaining long-term cycling stability. This work supports the theoretical basis and technical support for the development and extension studies of new vanadium-based electrode materials. NVO-AVO for the first time, a promising new cathode material for high-performance AZIBs is designed. The experimental results show that the NVO-AVO composite can exert the synergistic effect of orthorhombic AlxV2O5 and monoclinic Na2V6O16 center dot 3H2O with fast Zn2+ kinetics. By combining a series of ex situ and in situ complementary techniques, the zinc storage mechanism of NVO-AVO cathode and its intrinsic relationship with the electrochemical performance is revealed.image